1. Field of the Invention
This invention relates to a plastic buckle provided with a means for adjusting the length of a strap of suitcases or harnesses or the like.
2. Prior Art Statement
Such a plastic buckle as described above provided with means to adjust the length of a strap has been disclosed in Japanese Patent Public Disclosure No. SHO 54(1979)-144244. Describing this known buckle with reference to FIG. 12, the buckle 1 is provided on the inner surfaces of two side members 2 with an upper bar 3 and a lower bar 4 which are offset relative to each other and which have respective angled portions 5, 6 spaced away from each other by a distance that is smaller than the thickness of a strap B.
With this conventional buckle 1, attaching the strap B was extremely troublesome. Specifically, attaching the strap B required that it be inserted in the space between the bars 3 and 4. However, the opposed angled portions 5, 6 of the bars 3 and 4 narrowed the space, which made it very difficult to insert the strap B and severely limited the direction in which it could be inserted.
The conventional buckle 1 also has the defect that, if the strap B or the buckle itself is pulled in a wrong direction, the strap B is loosened and readily slips out. The strap B does not become loose and slip out while the strap B and the buckle 1 are maintained more or less horizontally, but pulling the trailing end portion of the strap B directly downward (i.e., in the direction indicated by b in FIG. 12) or lifting up the buckle itself extends the strap B in a straight line between the bars 3 and 4, which is a state in which the strap B can readily slip out.
When the conventional buckle is used on the seat strap of baby carriage, for example, because the strap cannot be tightened against the body of the infant the belt is often fastened with a certain amount of slackness. Because of this, the infant playing with the buckle and the movement of the infant's body pulling the strap in all directions can change the angle formed by the strap and the buckle, leading to further loosening of the strap and, in extreme cases, even to the strap becoming completely unbuckled, which is undesirable from the viewpoint of safety.